Who's Who at NASA

NTB: Since August 2006 you’ve been the Director of NASA’s Planetary Science Division. What is the Planetary Science Division, and how does it contribute to NASA’s overall mission?

Dr. Green: NASA’s Planetary Science Division is really all about understanding the origins and evolution of the solar system and looking for life beyond Earth. In other words, what are the conditions that could provide a habitat for life, and is there life on other planets or other parts of our solar system, perhaps even moons? And finally, understanding the environment well enough to determine what the hazards are for human habitability as we move into the solar system.

Now, that’s our broad objectives and goals. We accomplish that through a variety of spectacular missions. We have missions at many locations in our solar system, and in this next year we’re going to have some really unbelievable milestones. In fact, in November 2010 we will have one of our spacecraft named “EPOXI” – it used to be the Deep Impact spacecraft but now we’re retargeting it to another comet – fly by Comet Hartley 2.

In [early 2011] we’re going to fly by another comet with the Stardust spacecraft that we’ve renamed “Stardust NExT,” and that comet is Temple 1. Now Temple 1 we’ve already been by with Deep Impact and we’ve had an impacter on it. But with Stardust we’re going to fly by Temple 1 and we’re hopefully going to see the impact region. In addition to that we’ll be able to see that comet after it’s gone by the sun through its sublimation phase and really determine what does a comet do in terms of how it sublimates and how it emits the material that it holds out into the solar wind and, therefore, out into the solar system. So, two fabulous comet encounters are coming up.

In addition to that, in March 2011 is our MESSENGER spacecraft is going to get into orbit around Mercury. Mercury is a fabulous planet! We’ve flown by it now three times with MESSENGER and several times prior to that in the 1960s and early 70s with one of the Mariners. MESSENGER will get into orbit and be able to study that body like we’ve never done before. Mercury is a little bit bigger than our moon. It’s a small terrestrial planet, but it is extremely dense. In fact, it almost has the same density as Earth, even though it’s much, much smaller. The core of Mercury, we now understand, is larger than the core of the Earth. Now these are really puzzling things, and we hope that by getting into orbit and really studying it for two Mercury years or more, we will really be able to understand how that planet formed so close to the sun and why these properties are so unusual about it.

In addition to that, in July of 2011 we have another spacecraft called “Dawn” that is going to get into orbit around a fabulous asteroid called “Vesta.” Vesta is an enormous asteroid more than 500 kilometers in diameter, so it is quite a fascinating asteroid. It’s in the inner belt, and we will be in orbit for approximately a year before we then break that orbit and go on to the biggest asteroid, called “Ceres.” Then we’ll have 3 launches: in August (2011) Juno will be launched and going to Jupiter; in September (2011) Grail will be launched going to the moon; in November (2011) MSL – the Mars Science Laboratory – will be launched and going to Mars; and then within nine-or-so months after that it will land on Mars. So we have a litany of some fabulous activities that are going to happen. I believe that after these milestones have been accomplished and the data returned, we’ll see some fabulous science discoveries come out of it.

NTB: As you just noted, a large part of the Planetary Science Division’s focus is the search for life – or some evidence of life – elsewhere in our solar system, such as Mars, or the moons of Jupiter, and other bodies like these comets and asteroids you’ve been talking about. In the grand scheme of things, why is the search for life on other planets so important to NASA?

Dr. Green: Well, the search for life is really a fundamental question that we, I believe, as humans are innately drawn towards. We are quite interested to determine how unique this planet is. Obviously there’s nothing like Planet Earth in our solar system. But understanding how life might occur beyond Earth is really taking a good look at what the habitable conditions for life are in our own solar system.

Now, as I mentioned, we have some fabulous missions going to locations that will move us closer to understanding the habitability of Mars and other locations, but also whether there might be life there. MSL – the Mars Science Laboratory – is a perfect example of that. MSL is quite the astrobiology laboratory. It has the ability to make a variety of measurements. One measurement that we’re quite interested in is following up our new discovery that Mars is emitting methane. Methane can be emitted biologically of course; everyone is well-aware of that. But it can also be generated, as we call it, abiotically; in other words, with non-biological processes. So, by looking at the isotopes of methane, MSL will give us an indication of whether that methane is being generated by life on Mars or not.

We’re now doing research in the outer part of our solar system – places like Europa. Europa is just a fabulous, unbelievable moon of Jupiter. Europa is fairly large, about the size of Earth’s moon. It has a very hefty ice crust all around it and we now know that it has more water below that ice crust than the Earth has. It looks like it’s a potentially habitable environment because of the energies that might be associated with keeping the ice in liquid form below the ice shell and potential sources of food and other organics. It really is a very intriguing environment. We really need to follow up with a future mission to Europa.

So, the life question is of natural interest, and in planetary science it is all about looking at our own planetary systems and bodies to determine their habitability, and I think we’re in store for more really fantastic surprises.

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